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Pool as a Pond?


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Thank you, DP.


From what I hear from those who have all of the types in their ponds, the general hardiness of koi lies somewhere between pond-type goldfish and fancy goldfish.  The biggest difference between the species comes in tolerance of temperature extremes -- hot or cold.   This probably results from the much greater oxygen requirement of koi since warm water holds less oxygen and lack of oxygen under ice can lead to winter fish kills.  This, in turn, may result from their larger size.  The less mutated varieties of fancies can tolerate much warmer water than koi, and do as well as koi under ice.

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I could give you a bunch of references to aquaculture research, but I will simply tell you my experience.  I have two in-ground ponds and at any given time anywhere from four to eight container ponds depending on how many excess youngsters I have.  All of my ponds receive the same maintenance, 10% of the pond volume of fresh water dripped in daily, filter volume equal to at least 10% of the pond volume. All have phytofiltration, primarily plants growing in the top of filters. The ponds range from 8 inches to 30 inches deep.  My experience says that-- in my yard-- the shallower the pond, the healthier the fish.  My largest, deepest, and most lightly stocked pond is the one I think of as the "death pond".  I don't lose many fish, (the reason I have such a population problem) but most of those I lose are in the "big" pond.  I have never lost a fish in a pond 8" deep these are the "available" fish and I will never confess to the stocking level.


I currently have about 20 adult fancies (and a bunch of fry), all but one home-grown.  I have rehomed probably about 20 more adults.  The incidence of swim bladder disorder in my fancies is easy to compute -- zero%, since I have never had a floater.  My oldest fancies are in their fourth or fifth year and all move continuously when awake.  Fancies need swimming area much more than pond-type fish because their bodies become  heavier with every year. Swimming a lot helps keep them in shape and avoids the obesity that leads to swim bladder disorder.


Three or four years ago,  when I had a huge excess of baby fish and virtually all survived, I had to put all my long-bodied fish into a couple of stock tanks.  They had the same surface area, but one was a 50 gallon 1 foot deep and the other a 2 foot deep 100 gallon.  I put the littlest ones into the 50 gallon tank and the bigger ones into the 100 gallon.  At least 2/3 of the total number of fish were in the 50 gallon but the fish load was about the same.  A year later, the fish in the two tanks were about the same size.  At this point it was clear the fish load in the shallow tank was much greater than in the deeper tank since most of the fish were the same size.   I added a filter to the small tank.  At about 2 years after I set them up, just before I finally succeeded in giving them all away, I had some deaths -- all in the 100 gallon.  Fortunately, that was just when I finally succeeded in giving them all away.


If you have an in-ground pond, the deeper the pond, the more stable the temperature.  The earth serves as a thermal sink.  However, with a pond totally above ground, unless you have thick insulation around the sides, pond temperature should be a function of volume, not depth.

I have enjoyed your posts in this thread. I don't feel like you need to post sources etc as you have established credibility of your own. I think we often have differing view points based partly on our large difference in climate zones as well as my increased frustration with fish that need to be babied for health reasons. My switch to a Koi only pond is not far off!


This is an oldie but if I could give you ONE piece of advice with going to a koi only pond. Make sure it is gravity fed filter with some type of settling chamber that is easily flushed. Putting in a 4" BD or multiple drains now will save you a ton of work and possibly heartache in the end.  

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